Code: The FHWA noise standard is a method
for predicting and assessing roadway traffic
noise impact.

Enforcement: This federal agency mandates that each state
is responsible for enforcing this standard or a similar standard.
The standard can vary from state to state, depending upon the individual
circumstances and various interpretations of the terminology. Contact
your local Department of Transportation or Acoustics.com to find
out more about your states official standard.

General Information: Noise from highway traffic is one of
the most intrusive and significant environmental noises found in
our world today. The FHWA standard is divided into two categories:
Type I and Type II projects.

Type I: According to the FHWA, this category describes a proposed federal or federal-aid project for the construction of a new highway or major physical alterations of an existing highway. Adherence to the standard is mandatory for Type I projects.

Type II: According to the FHWA, this category describes a project for the construction of noise abatement measures that are added to an existing highway with no major changes in the highway itself. Adherence to the standard is not mandatory for Type II projects, but a traffic noise analysis is required if federal funding of abatement measures is desired.

If you are working on a project that is close to a future freeway site, it is most likely the Department of Transportations responsibility to conduct noise tests and to protect your project from excessive traffic noise.

If you are working on a project close to an existing freeway, whether or not a standard is developed and enforced is the citys decision.

Strength: The FHWA grants the state a certain
amount of freedom to customize the noise standard based on their
individual needs. A noise study is a valuable tool to determine
if a particular project will be impacted by traffic noise. Armed
with this information, proper steps can be implemented to minimize
the risk of exposure to excessive noise.

Weakness: The FHWA study is a specialized prediction
model that must be conducted and calculated by a trained technician.
This standard only looks at the exterior noise on the ground floor
of a structure. There is no assessment required for interior noise
or for additional floors above the first floor. Because the standard
is not universally enforced, inconsistencies include:

Vastly different enforcement standards from city to city.

A lack of uniformity in abatement measures. If a freeway stretches through several cities, you will notice various wall heights throughout.